Forces (C4) Flashcards

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1
Q

SI newton

A

kgms^(-2) from F=ma

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2
Q

Define mass

A

A measure of the amount of matter in something

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3
Q

Define weight

A

The force with which gravity pulls

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4
Q

Where does weight act from

A

the centre of mass

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5
Q

What is the centre of mass

A

mean position of mass, centre of gravity

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6
Q

method of finding a centre of mass

A

Push in no gravitational field until no turning moments are introdruced

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7
Q

What can a plumb line do

A

Find the centre of gravity by hanging the object

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8
Q

What is a free body diagram

A

one that isolates one object and just labels all the forces acting on it

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9
Q

Name some classic free body forces (5)

A
Weight
Friction
Drag
Upthrust
Normal contact force (reaction)
Tension
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10
Q

What do all free body diagrams need?

A

Labelled arrows (scaled)

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11
Q

What is drag?

A

Frictional force in a fluid

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12
Q

What determines drag?

A
Cross sectional area 
shape
speed
texture of object
density of fluid
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13
Q

Drag is proportional to

A

speed squared

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14
Q

What equation calculates net force?

A

F=ma

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15
Q

What is the principle of moments?

A

If the sums of the clockwise and anticlockwise moments are equal then the object is in rotational equilibrium

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16
Q

What is it called when there are no net linear forces?

A

translational equilibrium

17
Q

What is a couple?

A

Pair of antiparallel forces that cause the object to spin without translational equilibrium as the forces are equal

18
Q

What is the moment of a couple called

A

torque

19
Q

What does the moment of a couple equal?

A

single Force times distance between them

20
Q

SI unit for density?

A

kg/m^3

21
Q

What is pressure measured in?

A

pascals

22
Q

How do fluids exert forces on a submerged objects

A

perpendicular to the surface

and increases with depth

23
Q

upthrust equals?

A

weight of the water displaced?

24
Q

What is neutral buoynacy?

A

When a submerged object has the same density so doesn’t float or sink